1. Field of the Invention
The present invention relates in general to a non-rotary cutting tool, and more particularly to such a non-rotary cutting tool that can be easily manufactured and used in a finishing step of a machining process.
2. Discussion of the Related Art
There is known a scroll compressor as one type of compressor which is used in a refrigeration or air conditioning system, for compressing a gas used as a refrigerant in the system. The scroll compressor is constructed to include a pair of scroll members which are arranged in an opposing manner with the scroll members being interfitted. The scroll members are given a relative orbiting motion with respect to each other, so that each of successive series of enclosed spaces defined by the scroll members progressively decreases in volume as it moves inwardly from a radially outer position to a central position. With the decrease in the volume of the enclosed space, a fluid such as a gas introduced into the enclosed space is compressed and is then discharged from the enclosed space.
FIG. 5A is a perspective view of a fixed scroll member 100 which is to be fixed to a housing (not shown) of the scroll compressor, while FIG. 5B is a perspective view of an orbiting scroll member 103 which is to be brought into meshing engagement with the fixed scroll member 100. The fixed scroll member 100 includes a base plate 101 and an involute or scroll wall 102 extending from the base plate 101 in a direction substantially perpendicular to the base plate 101. Similarly, the orbiting scroll member 103 includes a base plate 104 and an involute or scroll wall 105 extending from the base plate 104 in a direction substantially perpendicular to the base plate 104. In an operation of the scroll compressor, the orbiting scroll member 103 held in engagement with the fixed scroll member 100 is rotated relative to the fixed scroll member 100, as shown in FIG. 6, whereby the gas within each of the enclosed spaces is compressed and is then discharged from the enclosed space through a discharge port 106 formed through the central position of the base plate 101 of the fixed scroll member 100. In this instance, the compression efficiency is increased with an increase in degree of fluid tightness between the scroll walls 103, 105. Therefore, in a process of machining the scroll members 100, 103, it is necessary that the scroll walls 103, 105 be machined with a high degree of accuracy. In a conventional process of machining a scroll wall of a scroll member, as disclosed in JP-A-H11-336657 (publication of unexamined Japanese Patent Application laid open in 1999), its roughing, semi-finishing and finishing steps are carried out by using rotary cutting tools such as end mills.
In the conventional machining process, however, each end mill attached to a spindle of a machine tool through a holder tends to suffer from its “run out” while being rotated with the spindle. In a finishing step of a machining process, the run out of the end mill makes it impossible to obtain a sufficiently high degree of machining accuracy, which is required in machining of scroll walls of a scroll compressor, for assuring a sufficiently high degree of fluid tightness between the scroll walls and a sufficiently high degree of compression efficiency in the scroll compressor. The degree of fluid tightness is inevitably reduced with reduction in the accuracy of the machining of the scroll walls, thereby problematically making it difficult to obtain the sufficiently high degree of compression efficiency in the scroll compressor. Further, it is also difficult to obtain an end mill inherently suitable for finishing the scroll walls which require to be finished with a considerably high machining accuracy.